well the plot of DQ7 works like this,a bunch of kids find a temple with lots of broken plaque and you go around finding shards to repair these plaque,everytime you repair a plaque you get teleported in the past to a new island and each island has it's own plot
when you finaly solve the plot of a island (which 80% of the times involve killing some big baddie) that island appear in the present so you get to see what happened to the village after your adventures
you also need to explore the island in the present to get more shard to continue so you can unlock more island and basicaly this pattern repeat until you eventualy runs out of plaque to fix
one of the most annoying aspect it's that some shards are hidden pretty well and if you miss a shard you can't continue the game,sometimes you clear a dungeon in the past and then you are forced to redo the same dungeon on the present to acquire new shards to continue
but the most annoying aspect of the game is the job system,halfway trough the game your character gets the ability to learn new skills trough the job system,you pick a job,you fight a certain number of battles and *BAM* your character learn a new skill,the problem is that some skill are completly worthless (one of the thief skill just tell you the name of your current location) and some almost break the game (like the one that let you attack 4 times consecutively instead of 1) so ultimately the challenge of the game depends on how willing you are to read a job faq and/or grind